Abstract
A method that greatly improves the stability of the IHCP solution is presented. The two principal features of the method are first that the same time step is used to solve the direct and inverse problems. Secondly, the direct model is designed in order to lead to the best estimation according to the location of the sensors. The method is based on the decomposition of the dynamic part of the thermal field on the modal basis of the heat diffusion operator. The stability of the solution is improved by eliminating the modes whose time constants are smaller than the lag time; that is the time of diffusion from the heated surface to the nearest sensor. An interesting consequence is that the reduced model requires less computation time than the complete one in a sequential estimation procedure.